The aircraft manufacturing process involves precision fabrication and assembly of large components, such as fuselage shell structures and wings. The position and orientation of components during fabrication and assembly require demanding tolerances. To satisfy demanding tolerances, information about a given component, such as information about the dimensions (e.g., surface contour) of the component or information about the location/orientation of the component, must be very accurate.
Thus, optical dimensional metrology techniques are commonly employed during the aircraft manufacturing process. For example, laser trackers are commonly used to perform various positioning and measuring functions during aircraft assembly. By projecting a laser beam at an optical target mounted to the object being measured, a laser tracker (or other apparatus employing a laser for dimensional metrology) can perform measurements at very high resolution, and can provide very accurate geometric dimensional data.
Retroreflectors are commonly used as optical targets because they reflect light back toward the source of the light (e.g., the laser tracker). Various retroreflectors are presently available with relatively large acceptance angles. However, when a light source is outside of the acceptance angle, such as when multiple spaced apart laser trackers are measuring the same optical target, the retroreflector must be moved into better alignment with the light source. The process of orienting retroreflectors into alignment with light sources can be time consuming and, therefore, expensive, particularly when the object being measured is relatively large.
Accordingly, those skilled in the art continue with research and development efforts in the field of optical dimensional metrology.